Impedance and voltage dividers



May 14, 1963 w. E. VAN HORNE IMPEDANCE AND VOLTAGE DIVIDERS Filed July1'7, 1961 M w R 2 3 8 9 M w 7 a p a 9 J mm m w" m F 9 o 6 6 H 8 -7 9 l B5 II. J m F 0 FIG. 4 INVENTOR.

WILLIAM E.VAN HORNE ATTORNEY y 1963 w. E. VAN HORNE 3,090,001

IMPEDANCE AND VOLTAGE DIVIDERS Filed July 17, 1961 2 Sheets-Sheet 2 FIG.9

FIG. IO

INVENTOR.

WILLIAM E. VAN HORNE wmw ATTORN EY United States tent spanner IMPEDANCEAND VOLTAGE DIJIDERS William E. Van Horne, Columbus, Ohio, assignor toKeinath Instrument Company, Columbus, Ohio, a corporation of Ohio FiledJuly 17, 1961, Ser. No. 124,592

15 Claims. (Cl. 323-79) This invention relates to impedance and voltagedividers. It has to do especially with essentially stepwise electricaltapping of impedance segments in impedance and voltage dividers whereinat least substantially four times as many steps are obtained as thenumber of junctions between impedance segments to which connection ismade.

In apparatus where it is desired to provide a range of voltages orimpedances in a continuously variable manner, as in the volume controlof a radio or television set, it is customary to make sliding contactdirectly on an impedance element. The devices used are commonly known aspotentiometers and rheostats. Where it is desired to scan repeatedlyover a range of voltages or impedances, however, scanning in acontinuous manner generally is not feasible because the friction of themoving contact on the impedance element causes appreciable electricalnoise and soon wears out the potentiometer or rheostat. For suchpurposes, therefore, it is customary to use stepwise scanning throughthe range of impedances or voltages by means of fixed contacts connectedto spaced points on the impedance. The fixed contacts and the slidablecontact can all be made of materials having high conductivity and goodresistance to wear.

In a common form of such device the fixed contacts may be arranged in acircle as are the commutator segments in a motor or generator, and thesliding contact may be in the form of a brush such as is used in a motoror generator. Although the contacts connected to the impedance arereferred to above as the fixed contacts, in rotating devices such asthose mentioned above they would ordinarily be the contacts that move,and the brush would remain stationary. As far as the electrical circuitis concerned, however, it is immaterial which contact or contacts move,as long as there is relative sliding movement between them.

Because of various physical limitations and cost considerations, thereis a practical limit to the number of taps that can be employed instepwise electrical tapping devices. Where it is desired to divide agiven voltage or impedance range into a large number of discrete stepsit would be desirable in many cases to be able to provide more stepsthan the highest practical number of taps, or the highest practicalnumber of commutator segments, Whichever is the limiting factor. It isknown that the number of steps can be made substantially twice thenumber of taps where an impedance is provided between each tap and itsrespective contact. In a voltage divider circuit of this type, when themovable contact bridges two adjacent fixed contacts the voltage on themovable contact is midway between that of each fixed contact where theimpedances connecting the fixed contacts and their respective taps onthe main impedance are equal.

It has been found in the present invention that by providing a pluralityof movable contacts, properly staggered, the number of steps can beincreased to at least substantially four times the number of taps. Morespecifically where two movable contacts are used, the number of steps issubstantially four times the number of taps, where three are used thenumber of steps is substantially six times the number of taps, andsimilarly where more movable contacts are employed the number of stepsis substantially twice the number of movable contacts times the numberof taps.

In the drawings:

FIG. 1 is a schematic diagram illustrating a typical embodiment of thepresent invention.

FIG. 2 is a schematic diagram illustrating one of the principlesinvolved in the invention.

FIGS. 3-10 are semi-pictorial, schematic views, in the general nature ofgraphs, illustrating the principles of the staggered contacts in theinvention.

Referring to H6. 1, a typical electrical device of the impedance andvoltage divider type comprises a series impedance member 51 comprisingthe individual impedance segments 52-58. Where equally spacedessentially stepwise tapping is desired, the impedances 52-58 should allbe equal. Connected to the ends of the impedance member 51 and to thejunctions between successive segments 52-58 are a plurality ofimpedances 59-66 having impedances that are substantially equal to eachother; and preferably substantially higher than the impedances of thesegments 52-58, to avoid inequalities in the steps that might result ifthe impedances 59-66 were low enough relatively to provide a substantialreduction in the impedance between junctions of the impedance segments52-58 during times when certain of the adjacent impedances 59-66 areconnected together and thus shunt one or more of the segments 52-58. Theopposite ends of the impedances 59-66 are connected respectively toelectrical contacts 67-74.

The contacts 67-74 are all substantially equal in length andsubstantially equally spaced, preferably closely, from their adjacentcontacts. Thus the distances between the corresponding ends ofsuccessive contacts 67-74 are substantially equal. The electricalcontacts 67-74 are arranged so that together they form a contact surfacesuch as a plane or a cylindrical surface whereon a slidable contact canbe positioned and moved lengthwise relative to the surface, as isindicated by the arrow 75, to contact at least one of the electricalcontacts 67-74 at any position on the surface.

A pair of slidable contacts 76-77 are held, preferably with resilientmeans such as springs (not shown), at a fixed lengthwise spacing fromeach other along the contact surface 67-74; and are slidable relative tothe surface in either direction, as is indicated by the arrow 75. Thelength of each slidable contact member 76-77 is one-half the distancebetween the corresponding ends of successive contacts 67, 68; 68, 69;69, 70; etc. The distance between the nearest edges of the slidablecontacts 76, 77 is 1% times the distance between the corresponding endsof successive contacts 67, 68 etc.

One end of a coupling impedance 78 is connected to the slidable contact76, and the other end is connected to a point 80. One end of a couplingimpedance 79 is connected to the slidable contact 77, and the other endis connected to the point 80. One side of a capacitor 81 is connected toone end of the impedance member 51, and the other side is connected tothe point 80. One side of a capacitor 32 is connected to the oppositeend of the impedance member 51, and the other side is connected to thepoint 80. One side of a capacitor 83 is connected to the slidablecontact 76, and the other side is connected to the slidable contact 77.For convenience in discussion it will be considered that a potential ofseven volts is applied across the impedance member 51, and the voltageacross each impedance segment 52-58 thus is one volt, the potentials atthe various junctions being as indicated in FIG. 1, ignoring any slightloading effect from the brushes and associated impedances.

To understand the operation of the present invention it is helpful toconsider the diagram of FIG. 2, wherein E, E E E E represent voltages(potentials), 1,, I I 1,, represent currents, and R representsimpedance, which for simplicity will be considered to be =.E,,--RI

from which 1+ 2+ a+ Where no current passes the point at E and Thus thevoltage E is the arithmetic mean, or more loosely the average, of thevoltages E E E E If current is drawn through the point at E, as is thecase in some rheostat applications, the above equations do not applyexactly, and the voltage E is not precisely the arithmetic mean of theindividual voltages; but it is very close thereto. As long as theimpedances 59-66, 78, 79 are substantially larger than the impedances ofthe segments 52-58, the loading eifect is small and any variation fromthe above equations is negligible.

Where essentially stepwise electrical tapping is desired, the capacitors81-33 are omitted from the circuit of FIG. 1. Refer-ring to FIGS. 1 and3, the circuit of FIG. 1 without the capacitors 81-83 operates inaccordance with the following explanation.

In FIG. 3 the heavy vertical lines represent the insulation or spacebetween contacts in the contact surface, and the blank spaces betweenthe heavy vertical lines represent the contacts 76, 71, 72, '73, whichhave the potentials 3 volts, 4 volts, 5 volts, and 6 volts,respectively, as indicated, when not shorted to an adjacent contact. Theheavy horizontal lines represent the slidable contacts 76, 77, asindicated, at successive positions on the contacts 7fl-73. Consideringthe contacts 76, 77 to be moving uniformly to the right, with timeindicated in the vertical direction and increasing as one reads down onthe diagram, it is seen that just before time I the contact 76 was at apotential of 3.5 volts, the contact 77 was at a potential of 5 volts,and the point 80 thus was at a potential of 4.25 volts, the arithmeticmean between the voltages at the contacts 76, 77.

At time I the contact 77 makes connection with the contact 73 as well asthe contact 72, as is indicated by the heavy dot 84. This raises thepotential at the contact 77 to 5.5 volts, and the potential at the point80 thus is raised to 4.5 volts, since the contact 76 is still at thesame potential as it had just before the time I. At time K the contact'77 remains at the same potential, 5.5 volts, but the contact 76 breaksits connection with the contact 74), as is indicated by the heavy dot85, and thus its potential is increased to 4 volts, and the potential ofthe point 30 is increased to 4.75 volts. Similarly at time L, with thepotential of the contact 76 remaining the same, the potential at thecontact 77 increases one-half volt as it breaks connection with thecontact 72, as is indicated by the heavy dot 86, and the voltage at thepoint 80 is increased one-fourth volt to the new potential of 5 volts.In like manner, with the potential of the contact 77 remaining the same,the contact 76 at time M makes connection with the contact 72, as isindicated by the heavy dot 87, raising its potential by one-half voltand the potential of the point St} by one-fourth volt. Finally, at timeN the potential at the point 80 is raised another one-fourth volt insimilar manner, so that it is now at a potential one volt greater thanits potential at time I, the contacts 76, 77 being in the samecorresponding positions as they were at time I, but each at a one volthigher potential.

From FIGS. 1 and 3 and the above discussion, it is apparent that as thecontacts 76, 77 move together onefourth the distance between thecorresponding ends of successive contacts 67-74, one of the contacts 76,77 either makes or breaks a connection, and thus changes its potentialby one-half volt and the potential of the point 86 by one-fourth volt.The action is the same in either direction.

In FIG. 4, which is the same type of diagram as FIG. 3, with legends andreference numerals omitted for convenience, it is apparent that the sameaction takes place. In every movement of one-fourth the distance betweencorresponding ends of successive contacts 67-74 the contacts 76, 77 taketurns making or breaking a connection, thus raising one of theindividual voltages one-half volt, and the average voltage, at the point80, one-fourth volt. In FIG. 4 the spacing between the contacts 76, 77is three-fourths the distance between the corresponding ends ofsuccessive contacts 67-74. The action is similar for any spacing of anodd number of quarters of the distance between the corresponding ends ofsuccessive contacts 67-74. The spacing must be at least three-fourths ofthat distance, however. Otherwise three successive contacts 67-74- wouldbe shorted at the wrong time in some positions, and this would provide aconflicting action. In other words, the distance between the contacts76, 77 may be A, A, or any higher odd number of fourths of the distancebetween the corresponding ends of successive contacts 67-74. The lengthsof the contacts 76, 77 may be increased to 7 or any odd number of halvesof the distance between the corresponding ends of successive contacts67-74; since the action is the same as that described and illustrated inFIGS. 3 and 4, except that the longer contacts short out one or more ofthe contacts 67-74 in addition to those as indicated in FIGS. 3 and 4.The alternate making and breaking of connec tions with every movement ofone-fourth the distance between the corresponding ends of successivecontacts 67-74 still takes place, however, in the same manner asillustrated in FIGS. 3 and 4.

For three or more slidable contacts the spacing principle is the same,and may be generalized by stating that successive slidable contacts arespaced any number of halves times the distance between the correspondingends of successive contacts 67-74 plus an equally spaced or evenstaggering over such a half distance. In the case of three contacts, theclosest spacing is two-thirds of the distance between the correspondingends of successive contacts 67-74. Stated differently, this is onehalfthe aforementioned distance plus one-sixth of that distance; or stilldifferently, one-half the distance plus /3 of /2. This spacing isillustrated in FIG. 6.

From FIG. 6 it is apparent that every /6 distance of movement across acontact 67-74 causes one of the slidable contacts to make or break aconnection, and that the contacts take turns so that in every halfdistance of movement each has made or broken a connection. In the nexthalf distance of movement each slidable contact successively makes orbreaks (the opposite of what it did in the first half distance ofmovement); bringing the slidable contacts back to the same correspondingposition as before the movement, but with each moved over the length ofone contact 67-74.

FIGS. 5 and 7 illustrate other convenient spacings for three slidablecontacts. In FIG. 5 the spacing is 1 /6 of the distance between thecorresponding ends of successive contacts 67-74; and in FIG. 7 thespacing is of the aforementioned distance, which is /2 plus 73 of /2.The staggering is equal in this case also because with the middlecontact spaced from the right-hand contact by /2 plus /3 of /2, and theleft-hand contact spaced from the middle contact by the same distance,the spacing between the left-hand contact and the right-hand contactthus is plus /3 of /2.

FIGS. 8-10 illustrate similar action where four slidable contacts areemployed. Here the spacing between successive slidable contacts is anynumber of halves of the distance between the corresponding ends ofsuccessive contacts 67-74 and fourths of that half distance such thatthe slidable contacts are staggered from the others by A1 and A; of thehalf distance. In FIG. 8 the spacing is 1 /8 of the distance between thecorresponding ends of successive contacts 67-74; in FIG. 9 the spacingis /8 of the aforementioned distance; and in FIG. 10 the spacing is ofthe aforementioned distance. From FIGS. 8-10 it is apparent that thesespacings provide uniform or even staggering such that for every movementof A; /1 of /2) the distance between the corresponding ends ofsuccessive contacts 67-74 the slidable contacts take turns making andbreaking connections, changing one of the four potentials by /2 volt,and the average potential by /8 volt.

To generalize, for any number of slidable contacts, the length of thecontacting surface of each slidable contact member in the lengthwiseslidable direction is equal to an odd integral multiple of one-half thedistance along the lengthwise slidable direction between thecorresponding ends of successive contacts 67-74, and the distance in thelengthwise slidable direction between the nearest edges of successiveslidable contacts is equal to an integral multiple of one-half thedistance along the lengthwise slidable direction between thecorresponding ends of successive contacts 67-74 plus a fraction of saidhalf distance, wherein the denominator of the fraction is the number ofsaid slidable contacts and the numerator is an integer such that the sumor" any said numerator plus any at least one other said numerator equalsan integer dillerent from the denominator and any multiple thereof. Theabove generalization is intended to indicate in more precise terms whatis meant by the equally spaced or even staggering within a halfdistance, as discussed above.

Referring back to FIG. 1, where it is desired to approach a continuousvoltage change rather than a stepwise change, the capacitors 81 and 82,connected between the point 80 and the ends of, or any other desiredpoints on, the impedance member 51, may be included in the circuit. Thevoltage across a capacitor cannot change instantaneously. It can changeonly gradually according to an exponential function, at a rate dependentupon the capacitance and other circuit values aifecting the timeconstant. The values of the capacitances 81, 82 can be chosen such thatthe time constants for the various positions of the slidable contacts76, 77 provide a fairly smooth, rather than a stepwise, change ofvoltage at the normal operating speed of the slidable contacts'76, '77.

Still further smoothing of the voltage at the point 8t as a function ofposition of the contacts 76, 77 moving at their normal speed can beprovided by including also the capacitor 83 connected between theslidable contacts 76, 77 (and with additional capacitors between otherpairs of contacts where more than two slidable contacts are employed),since the capacitor 83 similarly causes the potential between thecontacts 76, 77 to change gradually rather than instantaneously when oneof the contacts 76, '77 makes or breaks a connection. The capacitor 83should not be used between any contacts that are spaced less than thedistance between the corresponding ends of successive contacts 67-74,because shorting of the capacitors at certain positions would result inarcing.

Where it is desired that the stepwise tapping, or the smoothed tappingwith the capacitors added, is to be directly proportional to theposition of the slidable contacts (or as a function of time where theslidable contacts are moved at a uniform speed) the impedances of thesegments 52-58 should be equal and the staggering of the slidablecontacts should be even, as discussed above.

Where it is desired to obtain a difierent function of voltage orimpedance, either in a stepwise or a substantially continuous manner,the impedances of the segments 52- 58 may be made unequal in apredetermnied manner or the staggering of the slidable contacts maydiffer from that specified above, or both. Such variations areconsidered to be within the scope of this invention, but are toonumerous to be discussed individually. The impedances Sit-66 could evenbe made unequal in a predetermined manner to provide certain functions,as could the impedances '78, 79, and other coupling impedances Wheremore than two slidable contacts are employed. Ordinarily the impedancesegments 52-58, the impedances 59-66 and the coupling impedances 78, 79would be substantially pure resistances, especially in direct currentcircuits, but other types of impedance could be employed where desired.For convenience, only seven impedance segments 52-53 are shown inFIG. 1. In practice, a hundred or more such impedance segments are moretypical. Any desired number, of course, may be used.

While the forms of the invention herein disclosed constitute preferredembodiments, it is not intended to describe all of the possibleequivalent forms or ramifications of the invention. It will beunderstood that the words used are Words of description rather than oflimitation, and that various changes may be made without departing fromthe spirit or scope of the invention.

What is claimed is:

1. In an electrical device of the impedance divider and voltage dividertype comprising a plurality of impedance segments connected in series, aplurality of impedances each connected at one end to an end of a different one of said segments and at the opposite end to a differentelectrical contact, said electrical contacts being positioned in thesame sequence as said segment ends to which the ends of said impedancesare respectively connected, each said electrical contact beingpositioned closely adjacent to the next said contact but insulatedtherefrom, said electrical contacts together forming a contact surfaceWhereon a slidable contact can be positioned and moved lengthwiserelative to said surface to contact at least one said electrical contactat any posi tion thereon; means for making electrical connection to saidelectrical contacts to provide essentially stepwise electrical tappingof said impedance segments in at least substantially four times as manysteps as the number of said electrical contacts, comprising a pluralityof lengthwise fixedly-spaced and relatively lengthwise-sidable contactmembers, and means for providing relative lengthwise movement betweensaid contact members and said contact surface.

2. In an electrical device of the impedance divider and voltage dividertype comprising a plurality of impedance segments, having individualimpedances in accordance with a predetermined desired function,connected in series, a plurality of impedances, each connected at oneend to an end of a different one of said segments and at the oppositeend to a difierent electrical contact; each junction between saidsegments being connected to one end of one of said plurality ofimpedances and said electrical contacts being positioned in the samesequence as said junctions to which the ends of said impedances arerespectively connected, each said electrical contact being positionedclosely adjacent to the next said contact but insulated therefrom, saidelectrical contacts together forming a contact surface whereon aslidable contact can be positioned and moved lengthwise relative to saidsurface to contact at least one said electrical contact at any positionthereon; means for making electrical connection to said electricalcontacts to provide essentially stepwise electrical tapping of saidimpedance segments in at least substantially four times as many steps asthe number of said electrical contacts, comprising a plurality oflengthwise fixedly-spaced and rela tively lengthwise-slidable contactmembers; and means for providing relative lengthwise movement betweensaid contact members and said contact surface.

3. In an electrical device of the impedance divider and voltage dividertype comprising a plurality of impedance segments, each substantiallyequal in impedance, connected in series, a plurality of substantiallyequal impedances, each connected at one end to an end of a ditterent oneof said segments and at the opposite end to a different electricalcontact, each junction between said segments being connected to one endof one of said plurality of impedances and said electrical contactsbeing positioned in the same sequence as said junctions to which theends of said impedances are respectively connected, each said electricalcontact being positioned closely adjacent to the next said contact butinsulated therefrom, the distances between the corresponding ends ofsuccessive contacts being substantially equal, said electrical contactstogether forming a contact surface whereon a slidable contact can bepositioned and moved lengthwise relative to said surface to contact atleast one said electrical contact at any position thereon; means formaking electrical connection to said electrical contacts to provideequally spaced essentially stepwise electrical tapping of said impedancesegments in at least substantiaily four times as many steps as thenumber of said electrical contacts, comprising: a plurality oflengthwise fixedly-spaced and relatively lengthwise-slidable contactmembers; and means for providing relative lengthwise movement betweensaid contact members and said contact surface; the length of thecontacting surface of each said relatively slidable contact member inthe lengthwise slidable direction being equal to an odd integralmultiple of one-half the distance along said lengthwise slidabledirection between the corresponding ends of successive said electricalcontacts; said relatively slidable contact members being evenlystaggered between integral multiples of one-half said distance alongsaid lengthwise slidable direction between the corresponding ends ofsuccessive said electrical contacts.

4. In an electrical device of the impedance divider and voltage dividertype comprising a plurality of impedance segments, each substantiallyequal in impedance, connected in series, a plurality of substantiallequal impedances, each connected at one end to an end of a different oneof said segments and at the opposite end to a different electricalcontact, each junction between said segments being connected to one endof one of said plurality of impedances and said electrical contactsbeing positioned in the same sequence as said junctions to which theends of said impedances are respectively connected, each said electricalcontact being positioned closely adjacent to the next said contact butinsulated therefrom, the distances between the corresponding ends ofsuccessive contacts being substantially equal, said electrical contactstogether forming a contact surface whereon a slidable contact can bepositioned and moved lengthwise relative to said surface to contact atleast one said electrical contact at any position thereon; means formaking electrical connection to said electrical contacts to provideequally spaced essentially stepwise electrical tapping of said impedancesegments in at least substantially four times as many steps as thenumber of said electrical contacts, comprising: a plurality oflengthwise fixedly-spaced and relatively lengthwise-slidable contactmembers; means for providing relative lengthwise movement between saidcontact members and said contact surface; the length of the contactingsurface of each said relatively slidable contact member in thelengthwise slidable direction being equal to an odd integral multiple ofone-half the distance along said lengthwise slidable direction betweenthe corresponding ends of successive said electrical contacts; thedistance in said lengthwise slidable direction between the nearest edgesof successive said slidable contact-s being equal to an integralmultiple of one-half said distance along said lengthwise slidabledirection between the corresponding ends of successive said electricalcontacts, plus a fraction of said half distance, wherein the denominatorof said fraction is the number of said slidable contacts and thenumerator is an integer such that the sum of any said numerator plus anyat least one other said numerator equals an integer different from saiddenominator and any multiple thereof; a plurality of couplingimpedances, one for each said slidable contact, having impedancessubstantially equal to each other; each said coupling impedance beingconnected at one end to its respective said sliding contact and at theopposite end to the opposite end of each of the other said couplingimpedances; the junction of said opposite ends of said couplingimpedances being the point at which is provided said equally spacedessentially stepwise electrical tapping.

5. Apparatus according to claim 4, wherein each of said plurality ofsubstantially equal impedances has substantially higher impedance thaneach said impedance segment.

6. in an electrical device of the impedance divider and voltage dividertype comprising a plurality of impedance segments, each substantiallyequal in impedance, connected in series, a plurality of substantiallyequal impedances, each connected at one end to an end of a different oneof said segments and at the opposite end to a different electricalcontact, each junction between said segments being connected to one endof one of said plurality of impedances and said electrical contactsbeing positioned in the same sequence as said junctions to which theends of said impedances are respectively connected, each said electricalcontact being positioned closely adjacent to the next said contact butinsulated therefrom, the distances between the corresponding ends ofsuccessive contacts being substantially equal, said electrical contactstogether forming a contact surface whereon a slidable contact can bepositioned and moved lengthwise relative to said surface to contact atleast one said electrical contact at any position thereon; means formaking electrical connection to said electrical contacts to provideequally spaced essentially stepwise electrical tapping of said impedancesegments in substantially four times as many steps as the number of saidelectrical contacts, comprising: a pair of lengthwise fixedly-spaced andrelatively lengthwise-slidable contact members; means for providingrelative lengthwise movement between said contact members and saidcontact surface; the length of the contacting surface of each saidrelatively slidable contact member in the lengthwise slidable directionbeing equal to an odd integral multiple of one-half the distance alongsaid lengthwise slidable direction between the corresponding ends ofsuccessive said electrical contacts; the distance in said lengthwiseslidable direction between the nearest edges of said slidable contactsbeing equal to an integral multiple of one-half said distance along saidlengthwise slidable direction between the corresponding ends ofsuccessive said electrical contacts, plus one-fourth of said distance; apair of coupling impedances, one for each said slidable contact, havingimpedances substantially equal to each other; each said couplingimpedance being connected at one end to its respective said slidingcontact and at the opposite end to the opposite end of the other saidcoupling impedance; the junction of said opposite ends of said couplingimpedances being the point at which is provided said equally spacedessentially stepwise electrical tapping.

7. Apparatus according to claim 4, wherein said electrical connectionmaking means provides substantially six times as many steps as thenumber of said electrical contacts, wherein the number of saidrelatively slidable contact members is three, and wherein thedenominator of said fraction is three.

8. Apparatus according to claim 4, wherein said electrical connectionmaking means provides substantially six times as many steps as thenumber of said electrical contacts, wherein the number of saidrelatively slidable contact members is three, and wherein said fractionof said half distance is one-third.

9. Apparatus according to claim 4, wherein said electrical connectionmaking means provides substantiallysix times as many steps as the numberof said electrical contacts, wherein the number of said relativelyslidable contact members is three, and wherein said fraction of saidhalf distance is two-thirds.

10. Apparatus according to claim 4, wherein said electrical connectionmaking means provides substantially eight times as many steps as thenumber of said electrical contacts, wherein the number of saidrelatively slidable contact members is four, and wherein the denominatorof said fraction is four.

11. Apparatus according to claim 4, wherein said electrical connectionmaking means provides substantially eight times as many steps as thenumber of said electrical contacts, wherein the number of saidrelatively slidable contact members is four, and wherein said fractionof said half distance is one-fourth.

12. Apparatus according to claim 4, wherein said electrical connectionmaking means provides substantially eight times as many steps as thenumber of said electrical contacts, wherein the number of saidrelatively 10 slidable contact members is four, and wherein saidfraction of said half distance is three-fourths.

13. Apparatus according to claim 4, wherein at least one capacitor isconnected at one side to said junction of said coupling impedances andat the other side to an end of a different one of said series impedancesegments, to modify said essentially stepwise electrical tapping toprovide a substantially continuous variation where substantially uniformrelative lengthwise movement between said slidable contact members andsaid contact surface is provided.

14. Apparatus according to claim 4, wherein a pair of capacitors areconnected at one side to said junction of said coupling impedances andat the opposite side to the ends of said series impedance segments, tomodify said essentially stepwise electrical tapping to provide asubstantially continuous variation where substantially uniform relativelengthwise movement between said slidable contact members and saidcontact surface is provided.

15. Apparatus according to claim 4, including at least one capacitor,each said capacitor being connected across a difierent pair of saidrelatively slidable contact members.

No references cited.

1. IN AN ELECTRICAL DEVICE OF THE IMPEDANCE DIVIDER AND VOLTAGE DIVIDERTYPE COMPRISING A PLURALITY OF IMPEDANCE SEGMENTS CONNECTED IN SERIES, APLURALITY OF IMPEDANCES EACH CONNECTED AT ONE END TO AN END OF ADIFFERENT ONE OF SAID SEGMENTS AND AT THE OPPOSITE END TO A DIFFERENTELECTRICAL CONTACT, SAID ELECTRICAL CONTACTS BEING POSITIONED IN THESAME SEQUENCE AS SAID SEGMENT ENDS TO WHICH THE ENDS OF SAID IMPEDANCESARE RESPECTIVELY CONNECTED, EACH SAID ELECTRICAL CONTACT BEINGPOSITIONED CLOSELY ADJACENT TO THE NEXT SAID CONTACT BUT INSULATEDTHEREFROM, SAID ELECTRICAL CONTACTS TOGETHER FORMING A CONTACT SURFACEWHEREON A SLIDABLE CONTACT CAN BE POSITIONED AND MOVED LENGTHWISERELATIVE TO SAID SURFACE TO CONTACT AT LEAST ONE SAID ELECTRICAL CONTACTAT ANY POSITION THEREON; MEANS FOR MAKING ELECTRICAL CONNECTION TO SAIDELECTRICAL CONTACTS TO PROVIDE ESSENTIALLY STEPWISE ELECTRICAL TAPPINGOF SAID IMPEDANCE SEGMENTS IN AT LEAST SUBSTANTIALLY FOUR TIMES AS MANYSTEPS AS THE NUMBER OF SAID ELECTRICAL CONTACTS, COMPRISING A PLURALITYOF LENGTHWISE FIXEDLY-SPACED AND RELATIVELY LENGTHWISE-SIDABLE CONTACTMEMBERS, AND MEANS FOR PROVIDING RELATIVE LENGTH WISE MOVEMENT BETWEENSAID CONTACT MEMBERS AND SAID CONTACT SURFACE.